A manner of restricting a precoding matrix subset in a Long Term Evolution (LTE) system is restricting vectors that can be selected for W1. To be specific, a network device notifies a terminal of vectors that can be used by the terminal. If a specific vector is restricted, for example, a first vector is restricted, the first vector cannot appear in W1 when the terminal selects a precoding matrix. However, because vectors close to the first vector have relatively strong energy in a direction of the first vector, the network device usually cannot restrict use of only the first vector but also needs to restrict the vectors close to the first vector. If a prior-art method is used, vectors close to (or near) the first vector cannot appear in W1, either. In this case, a relatively large quantity of precoding matrices cannot be used, and consequently, system performance deteriorates.
In the New Radio Access Technology (NR), a type II precoding matrix is defined: W=W1×W2. Currently, no technology is related to a solution for restricting a precoding matrix subset of the Type II precoding matrix W=W1×W2. However, if the manner of restricting a precoding matrix in the LTE system is used, a relatively large quantity of precoding matrices cannot be used, and consequently, system performance deteriorates.